FIGS. 25 and 26 of the accompanying drawings illustrate the scum removal apparatus suggested by the inventor of the present invention. A generally rectangular sewage settling pool is provided with a plurality of, for example, four, sprocket shafts 200 extending in a widthwise direction of the sewage settling pool, a pair of sprocket wheels 201 mounted on each of the sprocket shafts 200 and generally endless, left-hand and right-hand chains trained around the sprocket wheels 201 on the sprocket shafts 200. In the suggested scum removal apparatus, some or all of the flights 203 secured to the chains 202 are driven together with the chains 202 to draw and remove the scum floating on the water surface in the sewage settling pool.
The scum removal apparatus includes a trough 205, a guide support sheet 206, a weir member 208 and a transmission mechanism 209. The trough 205 is in the form of an elongated member of a generally U-shaped cross-section opening upwardly and frontwardly and is fixedly disposed in the sewage settling pool so as to extend in the widthwise direction of the sewage settling pool.
The guide support sheet 206 is a band of rubber material of a length corresponding to that of the trough 205 and secured at one front side portion to an upper edge of a front wall of the trough 205 with the opposite rear side portion thereof protruding frontwardly from the front wall of the trough 205 so as to undergo undulation by the effect of its elastic deformation.
The weir member 208 is in the form of a generally elongated member having a front portion of a generally fight triangular hollow cross-section and a rear portion of a generally rectangular cross-section and has a base portion secured to the front side portion of the guide support sheet 206 so as to protrude outwardly therefrom so that, while supported by the guide support sheet 208, the weir member 206 can undergo a wavy motion above and below the fluid surface level 207 of sewage in the sewage settling pool.
It is the transmission mechanism 209 that drive the weir member 208 to move up and down with respect t the fluid surface level 207 in the sewage settling pool. This transmission mechanism 209 includes a rotary support shaft 210, a drive arm 211, and an operating arm 212. The rotary support shaft 210 is supported so as to extend widthwise of the sewage settling pool whereas the drive arm 211 is supported so as to extend from one end portion of the rotary support shaft 210 in a frontward direction substantially perpendicular to the rotary support shaft 210. The operating arm 212 is supported so as to extend in a direction counter to the direction of extension of the drive arm 211 and towards the trough 205 and is employed for each of the left-hand and right-hand sides of the sewage settling pool for the purpose of a stabilized operation. The drive arm 211 has a front end portion provided with a follow-up member 213.
The follow-up member 213 has a cam face defined at a bottom thereof, which cam face is constituted by two hill areas 213a and 213c and a dale area 213b positioned between these hill areas 213a and 213c. It is a roller (a drive unit) 214, protruding outwardly from one end of each flight (mud dragging member) 203, that drives the follow-up member 213 to actuate the drive arm 211 and the operating arm 212 to move the weir member 208 up and down with respect to the fluid surface level 207 of sewage in the sewage settling pool. This roller 214 is supported by a bracket secured to one end of the follow-up member 213 associated with each flight 203. Reference numeral 220 shown in FIGS. 25 and 26 represents a side seal (a sealing means) disposed between each side end of the weir member 208 and the adjacent side end of the trough 205 for avoiding a leakage of scum and water. This side seal is made of rubber material and is corrugated into a bellows between each side end of the weir member 203 and the adjacent side end of the trough 205 so that it can selectively expand and contract due to its elasticity in response to an undulating motion of both of the weir member 208 and the guide support sheet 206.
The suggested scum apparatus shown in FIGS. 25 and 26 operates in the following manner.
When a drive motor (not shown) installed on a ground outside the sewage settling pool is powered, the chains 202 are driven so that the flights 203 coupled with the chains 202 are driven so as to slowly circulate along a generally rectangular path as indicated by the arrows in FIGS. 25 and 26. The flights 203 being circulated successively scrape the sediment at the bottom of the sewage settling pool to guide it to a pit 221 in the bottom of the sewage settling pool so that the sediment so guided into the pit 221 can be subsequently discharged by a suitable pump (not shown) to the outside of the sewage settling pool.
Some of the flights 203 moving along a path adjacent the fluid surface level 207 during the circulatory motion thereof successively push the follow-up members 213 by means of the rollers 214. The rollers 214 are then brought into engagement with the follow-up members 213 in a first stage, first contacting the hill area 213a, then contacting the dale area 213b and finally contacting the hill area 213c, to thereby move the follow-up members 213 up and down. When each roller 214 is brought into engagement with the hill area 213a of the respective follow-up member 213, both of the follow-up member 213 and the associated drive arm 211 are lifted a considerable distance and, at the same time, the associated operating arm 212 is lowered, causing the weir member 208 to be pushed beneath the fluid surface level 207 by means of a rod 224.
At this time, the scum S floating on the top surface of the sewage, regardless of the size thereof, are guided into the trough 205 by the flow of water and is then discharged out from the trough 205. When each roller 214 is however brought into engagement with the dale area 213a of the respective follow-up member 213 in a second stage, both of the follow-up member 213 and the drive arm 211 are temporarily lowered while the associated operating arm 212 is lifted. Consequently, the weir member 208 having been lowered beneath the fluid surface level 207 is elevated a slight distance and, therefore, the amount of water component flowing over the weir member 208 into the trough 25 becomes small. Although the amount of the water component flowing over the weir member 208 is small, the velocity of flow of the water component becomes so high as to result in an increase of the force with which the scum S is drawn towards the trough 205. Therefore, scum lumps, small and large in size and/or floating near and a substantial distance away from the trough 205, can be smoothly drawn close towards the trough 205.
On the other hand, when each roller 214 is subsequently brought into engagement with the hill area 213c of the respective follow-up member 213 in a third stage, both of the follow-up member 213 and the drive arm 211 are again elevated and the associated operating arm 212 is lowered. Once this occurs, the weir member 208 is lowered to guide a substantial amount of the scum S, drawn close towards the trough 205 in the manner described above, into the trough 205. Thus, since the follow-up member 213 moves so as to perform the three stages, the draw of the scum S to throw it into the trough 205 can be performed with considerably high efficiency.
However, the above described scum removal apparatus has been found having the following problems.
Since the weir member 208 is supported by the guide support sheets 206 made of rubber material, the weir member 208 is held in a instable condition and, accordingly, the use of the plural operating arms 212 and also the use of the rotary support shaft 210 having a length corresponding to the width of the sewage settling pool are required, making the scum removal apparatus as a whole complicated in structure and costly to assembly. Also, since the operating performance of the weir member 208 is not consistent during the operation thereof, the amount of scum drawn thereby is not always constant.
Since the weir member 208 is in the form of a generally elongated member having a front portion of a generally right triangular hollow cross-section and a rear portion of a generally rectangular cross-section and is of one-piece construction, the molding thereof is very complicated and requires a high cost. Also, there is a problem in that, since the top of the front portion of the weir member 208 protrudes upwardly, some of the scum lumps tending to ride over the front portion of the weir member 208 is often entangled, thereby failing to ride over the front portion of the weir member 208. Also, since the rear portion of the weir member 208 is substantially in the form of a rectangular-sectioned plate, some of the scum lumps having ridden over the front portion of the weir member 208 tend to gather around the rear portion of the weir member 208 to such an extent that the weir member 208 may fail to operate properly and that an outer appearance tends to be spoiled.
Also, since the side seal 220 is in the form of bellows, not only does it require a high cost, but the attachment thereof is also complicated considerably.
Accordingly, the present invention has been devised to substantially eliminate the problems discussed above.
An object of the present invention is to make it possible to manufacture, at a reduced cost, the scum removal apparatus as a whole which is simple in structure and wherein the weir member can operate stably even though the operating arm employed is a single short rotary support shaft and also to stabilize the operating performance of the weir member so that the amount of scum drawn can be maintained constant.
The molding of the weir member can be achieved simply and at a reduced cost, and can be so designed as to allow the scum to easily ride over the weir member. Design has been made to avoid the scum from gathering around the weir member. Also, design has been made to avoid the scum from being accumulated on the way to thereby render the weir member to be comfortable to look at.
Design has also been made to render the seal means to be simple in structure and inexpensive and to permit the attachment thereof to be performed very simply.